This invention particularly relates to an improved method and apparatus for a photographic enlarger which provides for substantial improvements in obtaining critical focus of the image to be enlarged upon the photosensitive medium upon which the enlargement is to be produced. The invention is particularly useful where a substantial enlargement is required.
In the operation of conventional enlarger apparatus, the amount of enlargement is generally determined by positioning the enlarger lens and the original which is to be enlarged at an appropriate distance above the plane at which the photosensitive medium is to be positioned, with the knowledge that the enlarger lens will produce the desired degree of enlargement when proper focus is achieved by vertical lens adjustment. The projected image of the original object which is to be enlarged is focused upon the photosensitive medium plane by careful adjustment of the position of the lens between the original object and the photosensitive medium plane. The greater the enlargement, the closer the lens must be positioned to the original, and the more difficult it is to position the lens with the great precision necessary for achieving critical focus.
Accordingly, it is one object of the present invention to provide an improved method and apparatus for achieving critical focus, and which overcomes the problem of precision positioning of the lens in achieving critical focus.
Another object of the invention is to provide a method and apparatus for achieving critical focus which is much more accurate than any method and apparatus presently available for that purpose.
Another problem with the conventional method and apparatus for achieving critical focus of an enlarger is that the operator must view the projected image closely in order to judge when the critical focus has been achieved. This means getting his head down near the photosensitive medium plane. At the same time, in order to adjust the lens position, he must reach up above his head to the lens stage adjustment knob, which is an awkward and difficult position in which to adjust the lens position with great precision.
Accordingly, it is another object of the invention to provide an improved method and apparatus for achieving critical focus in a manner which is much easier for the operator, and which avoids the problem of reaching over his head, as described above.
In order to achieve the ultimate in sharpness in photographic enlargements, it is virtually essential to focus the emulsion surface of the object precisely upon the emulsion surface of the photographic medium upon which the enlargement is being produced. With present conventional photographic enlargement equipment, it is extremely difficult to achieve this degree of precision in focus.
Accordingly, it is another object of the invention to provide for critical focusing with greater accuracy than has previously been achievable, and which does focus the emulsion surface of the object upon the emulsion surface of the photosensitive material, when that is desired.
Further objects and advantages of the invention will be apparent from the following description and the accompanying drawings.